This invention relates to ductwork embodying a generally rectangular configuration, and more specifically, to an improved form of square corner design for ductwork of the type that is intended for use in applications wherein there is a need for the ductwork to withstand increasingly higher pressures, and wherein such pressures are likely to produce proportionally higher stiffener end reaction loads, e.g., end reaction loads that exceed two kips in magnitude.
There exist many applications in which ductwork is normally employed wherein the pressures to which the ductwork is subjected are relatively high. For purposes of this discussion, relatively high pressures are considered to be pressures having values on the order of 40" to 50" water gauge or higher. The latter pressures are to be contrasted with pressures of a magnitude of 20" to 25" water gauge, which are the values of pressure that have heretofore normally existed in ductwork applications of a similar type.
One type of application, wherein ductwork which is capable of being subjected to such relatively high pressures is needed, is in connection with the functioning of a utility-type steam power generation installation. In this type of application, such ductwork is principally utilized for purposes of channeling the flow from one location to another of substances which are in gaseous form. In the course of effecting this channeling of gas flows from one location to another, there is frequently need that the ductwork change directions one or more times. Further, each of these changes in direction results in the formation of a corner at those locations whereat a change in direction occurs. More specifically, the corners formed at these locations result from the interconnection thereat of sections of ductwork which extend in different directions. Oftentimes, these sections of ductwork extend perpendicular to each other, thereby occasioning the establishment of a right angle corner.
Heretofore, the ductwork that has been employed in the type of application referred to above has commonly consisted of metal plate having both a stated thickness and a stated width. However, in view now of the need for the ductwork to be able to accommodate the increasingly higher pressures referred to above, existing ductwork designs are no longer deemed to suffice. Thus, a need has been evidenced for a new and improved form of design for ductwork wherein a ductwork constructed in accordance therewith is both of sufficient size to enable the desired volume of gas flow to be passed therethrough, and is of a sufficient strength to satisfactorily withstand the increasingly higher pressures, i.e., 40" to 50" water gauge or higher, to which the ductwork will be subjected. To the extent that a ductwork constructed in accordance with such a new and improved form of design embodies physical dimensions that exceed those of existing ductwork, the former, in comparison to the latter, is more difficult to handle, as one would normally expect. That is, the manipulation which is required in order to effect the fabrication and/or assembly of the ductwork is more difficult to accomplish with the former than with the latter.
Generally speaking, the mode of assembly that has been followed in the case of ductwork embodying prior art forms of construction has been one wherein the resulting ductwork has had a generally rectangular configuration. More specifically, such prior art ductwork has embodied a four-sided form of construction with each of the four sides being joined to two of the other three remaining sides in such a manner as to have a substantially flush fit therewith. Further, each of the four sides is secured to the corresponding two of the other three remaining sides by means of an external weld, i.e., a weld that is located on the exterior surface of the ductwork.
In the case of ductwork constructed of three-sixteenth inch metal plate in accordance with the teachings of the prior art, i.e., constructed in the manner to which reference has been had hereinbefore, the welds that have been utilized for purposes of securing the four sides of the ductwork together have, generally speaking, been limited to welds having a maximum dimension of one-eighth inch. This limitation, as regards the matter of the size of these welds, is basically one that is inherently derived. That is, this weld size limitation is dictated principally by the thickness of the metal plate that is to be joined, as well as the matter of the positioning of the weld itself. However, although such a size limitation has inherently existed in the case of much of the ductwork constructed in accordance with the teachings of the prior art that has been employed heretofore, this limitation on weld size normally has been of no moment, insofar as concerns the matter of the structural integrity of such welds. Namely, the strength of such welds has been more than sufficient to adequately resist loadings that are applied to the ductwork, e.g., loadings of a magnitude of up to two kips in the case of the end reaction loadings to which the corners of such ductwork are subjected. Yet, on the other hand, note is made here of the fact that it is virtually impossible, under the circumstances that exist in the case of prior art forms of ductwork construction that embody welds on the external surface thereof, to specify a minimum dimension for each of the welds that are utilized therein. As a consequence, the welds employed in the case of such prior art ductwork do not meet the standards of what commonly is recognizable as a structural weld.
In an effort to meet the requirements imposed on ductwork that are to be subjected to the increasingly higher pressures which have been previously referred to hereinabove, various different modes of assembly vis-a-vis those which have been utilized heretofore by the prior art, have been suggested for purposes of effecting the construction of such higher pressure capacity ductwork. For the most part, however, the modes of assembly that have been proposed for employment for this purpose are in the nature of jury-rigged forms of construction. That is, they seem to embody forms of construction that have been virtually customized to meet the requirements of particular individual applications for ductwork of higher pressure capacity. To this end, the higher pressure capacity ductwork resulting from the utilization thereof of such jury-rigged forms of construction is disadvantageously characterized in a number of respects including, but not limited to, those enumerated below: the cost thereof, the ease of fabrication thereof, the structural integrity of the welds thereof, etc.
A need has thus been evidenced for a new and improved form of construction for ductwork capable of being utilized in applications wherein the ductwork will be subjected to relatively high pressures, e.g., pressures of 40" to 50" water gauge or higher, and wherein the ductwork embodies the following features of an advantageous nature. First, the mode of assembly of the ductwork is such as to enable economies to be realized in the course of the assembly thereof. Secondly, the welds utilized for purposes of effecting the joining together of the sides of the ductwork are capable of having minimum dimensions specified therefor. Thirdly, each of the welds employed in the ductwork is effected in such a manner as to be recognizable as a structural weld. Fourthly, the ductwork is strong enough to resist the high stiffener end reaction loads to which the corners thereof are subjected. Fifthly, the ductwork is flexible enough to make allowance for the occurrence of some stiffener vibration, particularly in applications wherein large high pressure fans are cooperatively associated with the ductwork such as in utility type steam power generation installations. In summary, it is important to note here that one of the principal difficulties that is encountered in connection with effecting the design of a ductwork that meets the above listed criteria is to provide a ductwork wherein the corners thereof are suitably constructed such as to be capable of sustaining the high end reaction loads that are applied thereto, while at the same time the ductwork including the corners thereof possess sufficient flexibility so as to be capable of accommodating the vibrational effects that inherently are experienced thereby.
It is, therefore, an object of the present invention to provide a new and improved square corner design for ductwork of the type that is employable for purposes of channeling the flow of gases from one location to another.
It is another object of the present invention to provide such a square corner design for ductwork which is particularly suited for use wherein a requirement exists for ductwork that is capable of withstanding pressures having values of 40" to 50" water gauge or higher.
It is still another object of the present invention to provide such a square corner design for ductwork which is particularly suited for use wherein a requirement exists for ductwork that has the capability of successfully resisting end reaction loads at the corners thereof which exceed two kips in magnitude.
A further object of the present invention is to provide such a square corner design for ductwork that is desirably characterized in that not only are the corners thereof capable of sustaining relatively high end reaction loads, but also the ductwork embodies sufficient flexibility to accommodate the vibrational effects that inherently are experienced thereby.
A still further object of the present invention is to provide such a square corner design for ductwork that for purposes of effecting the joining together of the sides thereof employs welds, which are capable of having the minimum dimensions thereof specified.
Yet another object of the present invention is to provide such a square corner design for ductwork wherein the sides thereof are joined by means of welds, and wherein each of these welds is recognizable as a structural weld.
Yet still another object of the present invention is to provide such a square corner design for ductwork wherein engineering as well as manufacturing economies are capable of being realized therewith in the course of the construction thereof.
Yet a further object of the present invention is to provide such a square corner design for ductwork which is advantaqeously characterized in the fact that it is easily assembled.